While use of the valve is not limited to oilfield water injection systems, it has been developed in connection with such systems; thus its advantages will be better understood by discussing the shortcomings of the valves heretofore used in that service.
It is conventional to use flapper check valves in water injection systems, due to the rapid erosion of the valve seat which takes place. The flapper valve has been chosen because the area of contact between valve and seat is relatively large when compared with alternatives, such as ball and dart valves.
However, even flapper check valves commonly fail very quickly in this service. By way of example, they usually involve springs which quickly corrode and break. Also, the seal between the flapper and the seat is not as effective as it might be and water erosion and corrision of the corner of the seat frequently occurs in a few months.
As a further disadvantage, the commonly used flapper valves, of which I am aware, normally have a valve seat formed integrally in the wall of the valve body; because the seat is not removable, reconditioning of it is difficult and expensive. Since these valves in some cases have to be repaired every two or three months, the cost of maintenance is accordingly high.
There is thus a need for a valve which provides improved durability and ease of reconditioning.